In this video, we're going to begin our lesson on types of cell signaling. And so what's important to note is that communication between cells of multicellular organisms is really important for maintaining the organism's homeostasis. And recall that homeostasis is basically just the idea of maintaining internal conditions within the cell. And this is really important for organisms. So communication between cells is going to occur via cell signaling. And communication via cell signaling can occur in really 2 different types of ways. It can occur directly or it could occur indirectly. And so moving forward, we're going to talk about direct cell signaling and indirect cell signaling in their own separate videos. But we're going to start with the direct cell signaling. So I'll see you all in our next video to talk about that.
Types of Cell Signaling - Online Tutor, Practice Problems & Exam Prep
Types of Cell Signaling
Video transcript
Direct Cell Signaling
Video transcript
In this video, we're going to introduce direct cell signaling. And so direct cell signaling, as its name implies, is going to be local signaling between cells that are in direct contact with each other. And so recall from our previous lesson videos that neighboring cells are able to directly communicate via different types of cell junctions. And so notice down below in our image over here on the left-hand side, we're showing you an example of how cell junctions can be used for direct cell signaling. And so recall that gap junctions are junctions that connect the cytoplasm of 2 animal cells. And so what you'll notice is that these gap junctions, these proteins here, they create a gap between the two cells where the cells are able to exchange nutrients and exchange signaling molecules with each other to directly communicate, and notice that they are in direct physical contact here with these gap junctions. Now over here notice that we have plant cells and plant cells use plasmodesmata as their version of gap junctions that connects their cytoplasm. And so here, we're showing you plasmodesmata, which, again, is gonna connect the cytoplasm of plant cells, allowing them to exchange nutrients, materials, and signaling molecules so that they can be in direct contact and signal and communicate with each other. Now, cell to cell recognition is going to be when cells make direct contact via membrane proteins. And so, these membrane proteins ultimately are gonna cause a cellular response. And so if we take a look at our image down below over here, cell to cell recognition, notice that we have, 2 cells that are in direct contact, this cell here and this cell over here, and notice that they have membrane proteins. This one has green membrane proteins and the other one has purple membrane proteins here. And so what you'll notice is that with cell to cell recognition, a cell is able to recognize the proteins on the surface of another cell, is able to recognize membrane proteins. And so here on the left-hand side, what we have is our signaling cell, and on the right-hand side what we have is the target cell. And the reason this is the target cell is because, ultimately, this is where the cell response is being generated. And so we could say this cell is signaling to this cell to respond. And so this here concludes our introduction to direct cell signaling. And in our next lesson video, we'll talk about indirect cell signaling. So I'll see you all in that video.
Indirect Cell Signaling: Paracrine vs Endocrine
Video transcript
In this video, we're going to introduce indirect cell signaling and compare and contrast paracrine versus endocrine hormones. Indirect cell signaling, unlike direct cell signaling, and as its name implies, is distant signaling between cells that are not in direct contact with each other, and it commonly uses hormones. Hormones are defined as signaling molecules that are released by a cell or gland and can travel and affect distant cells in other areas. There are 2 types of hormones that we're going to mention here: the paracrine hormones and the endocrine hormones. Paracrine hormones are hormones that travel very short distances and only act on nearby cells in the vicinity of their synthesis, whereas endocrine hormones are specifically released into the bloodstream. Once endocrine hormones are released into the bloodstream, they can travel long distances to their target cell and still allow for cell signaling.
Let's take a look at our image below to get a better understanding of indirect cell signaling. Notice that in our image, we have this top half and this bottom half. The top half, circled in yellow, shows paracrine hormones, indicating indirect signaling using paracrine hormones. Paracrine hormones travel short distances. One thing to note is that the signaling cell here is not in direct contact with the target cell; there is a gap between them. With paracrine hormones, these signaling molecules only travel a short distance to get to the target cell and trigger a cell response.
Now, in the bottom half of the image, we are showing indirect signaling using endocrine hormones. Endocrine hormones are secreted into the bloodstream and ultimately travel long distances to the target cell. Notice over here on the left-hand side, we have the signaling cell secreting endocrine hormones into the bloodstream. Once the endocrine hormones have been secreted into the bloodstream, they can travel much further distances. Notice there's a larger distance here between the two cells as compared to paracrine hormones. These endocrine hormones end up being received by the target cell for a cell response to be initiated.
This concludes our introduction to indirect cell signaling and the difference between paracrine and endocrine hormones, and we'll be able to get some practice applying these concepts as we move forward in our course. So, I'll see you all in our next video.
Paracrine signaling is characterized by signaling molecules (ligands) that are _______:
Cortisol is a stress hormone created by the adrenal glands which can affect many tissues throughout the body. How is cortisol able to reach target cells that are far from the adrenal glands?
Synaptic Cell Signaling
Video transcript
In this video, we're going to introduce synaptic cell signaling. Synaptic cell signaling occurs when specific cells release neurotransmitters across a synapse, activating a target cell. Neurotransmitters can be defined as chemicals released by the end of a neuron, or in other words, a nerve cell, to transmit a signal or convert the signal into a cell response. A synapse is defined as a small junction or region between the end of a nerve cell or the end of a neuron and another cell.
Let's take a look at our image down below to get a better understanding of synaptic cell signaling. Notice up above, this is showing the very end of a neuron; recall, the neuron is a nerve cell. Notice that at the very end of this neuron, there are these little vesicles or membrane bubbles that contain neurotransmitters. These little purple circles you see are the neurotransmitters. These neurotransmitters can be released into this region here, colored in green, which is the synapse. The synapse is, again, the junction or the region between the very end of a neuron and another cell down here, which is our target cell.
The neurotransmitters will help transmit the signal or convert the signal into a cell response. Notice that the neurotransmitter will bind to a receptor embedded in the target cell's membrane, and that receptor ultimately is going to trigger signal transduction, a series of events that ultimately leads to the cell response. Synaptic cell signaling is a form of paracrine signaling since the neurotransmitter travels short distances across the synapse. This specific type of paracrine signaling occurs between a neuron and another target cell.
This here concludes our introduction to synaptic cell signaling, and we'll be able to get some practice as we move forward in our course. I'll see you all in our next video.
Which of the following types of signaling is represented in the figure?